Preparation And Electrical Properties Of Ordered Porous Tantalum Foil Anode Materials

In recent years,with the rapid development of military industry and the continuous improvement of equipment information level,tantalum electrolytic capacitor demand for tantalum electrolytic capacitor also grows rapidly as the overall equipment develops towards high precision and high reliability.Traditional tantalum electrolytic capacitors were manufactured by tantalum powder high pressure pressing block,high temperature sintering,coating and other processes.Such preparation process has insurmountable difficulties such as disorganized and uneven formation of holes and great difficulty in sintering,which makes it difficult for cathode materials to penetrate,capacitor cannot be extracted and high voltage resistant.Therefore,it is urgent to make a breakthrough in the manufacturing principle and develop a new generation of tantalum capacitor manufacturing technology to achieve high specific capacitance and high working voltage.In this thesis,a novel foil anode material for tantalum electrolytic capacitors with high specific capacitance and high voltage resistance was prepared by combining pulsed power electrochemical etching technology and laser surface cladding technology.In this thesis,porous anode materials were prepared by electrochemical etching of tantalum foils with a mixture of Li Cl-methanol and water in pulsed power supply and ultrasonic environment.The corrosion parameters were systematically studied by means of scanning electron microscopy（SEM）morphology characterization,mercury injection test,Tafel polarization curve test,Nyquist curve test and digital bridge ratio capacitance measurement,including:Corrosion voltage,corrosion time,electrolyte composition,frequency,duty cycle and experimental temperature.In order to further improve the specific capacitance,laser cladding iron powder technology was introduced to increase the corrosion site.The further effects of laser power,scanning speed and iron powder uniformity on the morphology and electrical properties were systematically studied.The feasibility of the experiment was verified by XRD and XPS characterization.The results show that the uniform porous anode structure,high specific capacitance and high voltage resistance of tantalum electrolytic capacitor anode prepared by the combination of pulsed power electrochemical corrosion technology and laser cladding technology has been realized.Using the corrosion voltage of 2.3 V,the frequency of 50Hz and the duty cycle of 30%,the tantalum foil was etched for 26 min in the electrolyte with the concentration of 3 wt%and water content of 0.6 Vol%,and then formed at 100V in 0.1 wt%H₃PO₄solution.The corroded and oxidized tantalum foil anode was then tested in 1 M H2SO4,and a maximum specific capacitance of 85 n F/mm²was achieved.Compared with the optical foil（18.8 n F/mm²）,the specific capacitance of the anode material after electrochemical corrosion was increased by 4.5 times.Meanwhile,the cladding iron powder by 1064 nm laser with 13.5 W laser power and 120 mm/s scanning speed,after the best parameters of the above corrosion,whose specific capacitance can be further improved.After 100 V formation,the specific electric capacity reached 155.1 n F/mm²,which is 8 times of the light foil.After optimizing the uniformity of the iron powder,the specific capacitance of 200.5 n F/mm²can be obtained,which is 10.7 times that of the light foil.The uniform porous structure of foil-type anode material for tantalum electrolytic capacitors prepared by the above research was obtained,which realized high specific capacitance and high voltage resistance.It is expected that this material with uniform porous structure,high specific capacitance and high voltage resistance has a wide range of applications in military,aerospace and micro flexible devices.